Reversing arrangement in two-stroke engines



June 3, 1952 o. PETERSEN 2,599,479

REVERSING ARRANGEMENT IN TWO-STROKE ENGINES Filed Feb. 4, 1947 2 SHEETS-SHEET 1 Fig'. 1

nasca "cr-oon June 3, 1952 o. PETERSEN REVERSING ARRANGEMENT IN TWO-STROKE ENGINES Filed Feb. 4, 1947 2 SHEETS- SHEET 2 /NVENTUR OV@ Pe/cfjfm 4 TTI-ORN EY Patented `l'une 3, 1952 R'EVERSINGARRANGEMENT 1N Twos'rRoKE ENGINES Ove Petersen, Gentofte, Denmark l Applicaton'February 4, 1947, Serial'No. 726,407 In Denmark February 6, 1946 (Cl. 12S- 41) 1 Claim.

Reversing of two stroke internal combustion engines of the kind Where fuel injection pumps and exhaust valves are controlled from a mutual cam shaft furnished with cam disks requires mutually different angular displacements of the times of control for fuel pumps and exhaust valves in relation to the dead point positions of the crank shaft. These angular displacements have hitherto in engines of the said kind been brought about by turning of the cam disks in relation to the crank shaft, but as the cam disks as already mentioned are to be turned mutually different angles it is not possible to effect the reversing only by turning the cam shaft as a whole in relation to the crank shaft, butl means must furthermore be provided for turning one or both sets of cams in relation to the cam shaft. This is rather complicated and also gives rise to an increase in cost of the engine, which is especially felt in multicylinder engines. In practice it is moreover necessary to put up with a form of the cams of the exhaust valves that is to some degree unsatisfactory for the working of the engine in order that the cams may be used for both directions of rotation. For various reasons the cams are somewhat longer than necessary for the exhaust process, whereby the exhaust valve is held open unnecessarily long, so that scavenging air is wasted.

The purpose of this invention is to remedy these drawbacks and procure an improved reversing arrangement in two stroke engines, in which the fuel pumps and the exhaust valves are controlled by a mutual camshaft and have mutually different angles of advance in relation to the dead point position of the crank. In accordance with the invention the alterations in angles necessary for the reversing are eected collectively for all fuel injection pumps and exhaust valves by displacing their rollers or'tappets in relation to the respective cams transversely to the cam shaft, while the cams themselves preserve their angular position in relation to the cranks of the respective cylinders unaltered.

Engines are known in which a cut-off slide valve in the pressure pipe from a fuel pumpdriven by the compression pressure to the injection valve is controlled from a negative cam on a cam shaft by means of an arm with a roller, which may be displaced transversely to the cam shaft for the regulation of the opening point of the cutting-off slide valve and thereby for the alteration of the injection point. In accordance with the invention is, however, attained a complete reversing of an engine, the cam shaft of 2 which controls both fuel pumps and exhaust valves, while being perfectly at liberty to adapt the alterations in the angles of advance in the optimum way and to shape the cams in the Way thatwill be the most favourable for the running of the engine, all without it being necessary to use complicated and expensive arrangements for a mutually different angular turning of the cams.

In an embodiment of the invention herein shown and described by way of example, the said tappets or rollers are displaced from a position on one side of the dead center point of the respective cams to a position symmetrical therewith on the other side of the said point upon reversing of the engine. When the cam itself is then made symmetrical around the dead center point, the engine will run under exactly the same conditions in both directions of rotation.

All rollers or tappets which are to be displaced during the reversing are preferably in accordance with the invention connected to arms on a shaft running parallel to the cam shaft, the length of these arms being so adapted that by turning of the shaft between two-certain positions the individual rollers or tappets will get exactly the transverse displacement in relation to the cam shaft which produces the angular displacement desired.

The invention is illustrated in the drawing in which Fig. 1 is a schematic view partly in section showing the driving means for a fuel injection pump for a reversible engine in accordance with the invention, and V Fig. 2 is a similar view showing the driving means for an exhaust valve belonging to the same engine but in a different position as describedbelow.

In the drawing l schematically designates part of a cylinder in the engine that has not been further shown, and 2 a cam shaft running in suitable bearings alongside the engine, which shaft drives all the fuel injection pumps and exhaust valves, the shaft 2 outside each cylinder having a set of cams serving for this purpose and comprising a fuel pump cam 3 and an exhaust cam I4.

The fuel pump cam 3 is shown in Fig. 1 in the position which it takes up when the fuel injection commences, a roller 5 on the end of a short tappet 6, which is hinged to a crosshead 1 in the pump case, having started travelling on the inclining face of the cam. Hereby the crosshead I drives a pump piston 8 into the rpumping cyl- 3 inder 9, from which the fuel is led through a pipe I to the injection valve.

The roller is held in the position shown by a link I3 which is hinged to an arm I2 on a rotatable control shaft II journalled parallel to the cam shaft 2. By turning the shaft Il so that the arm I2 is made to take up the position shown in dotted lines the roller 5 is moved to the position shown in dotted lines. and the dimensions have been chosen so that the angular displacement v attained hereby of the roller in relation to the line of symmetry 4 of the cam will give a fuel injection exactly at the proper angle of advance in the new direction of rotation.

In Fig. 2 the exhaust cam I4 is shown in the position it takes up when the crank of the respective cylinder is in its lower dead center position, the cam shaft 2 thus being in a different position from that shown in Fig. 1. The exhaust valve is held open by a roller I6 on a tappet Il which is raised by the cam and thereby in the usual way holds the valve in its open position by means of a rocker arm I8.

The roller I6 is held in its place by a link 20 which is hinged to an arm I9 on the control shaft II. The dimensions are such that on the turning of the shaft I I through the same angle as was mentioned above in connection with Fig. 1 the roller I6 is displaced an angle u in relation to the line of symmetry I5 of the exhaust cam which gives the proper angular position for running in the new direction of rotation. The angle of displacement u may within wide limits be chosen as desired, and therefore it is possible to give the cam I4 the shape and extent which is most expedient for the exhaust process proper and there is no need of deviating from this out of regard to the fact that the engine must be able to run in both directions of rotation. It is most advantageous but not necessary that the cam is symmetric around its center line, whereby an exactly uniform control of the exhaust in both directions of rotation is attained.

The means serving for simultaneous displacement of the rollers and tappets to be taken into consideration in relation to the cam shaft may be arranged in other ways than that shown, the essential feature being only that they are able to give the rollers or tappets such displacements in relation to the cams co-operating therewith that While taking the form and extent of the latter into consideration the angles of advance desired are attained for the commencement of the injection and exhaust in both directions of rotation. In the example shown the suction stroke of the fuel pump immediately precedes the pressure stroke and is of the same duration as the latter. In some cases it may be desirable or necessary to take this into account by proportioning the admission openings and the supply pipes of the pumping cylinder somewhat larger than ordinarily.

I claim:

In a two stroke internal combustion engine, a cam shaft rotating in synchronism with the engine, a fuel pump cam on said shaft, said cam having symmetrical ascending and descending operating cam surfaces substantially joined at their lower ends and a circular cam surface concentric with said shaft joining their upper ends, an exhaust valve cam on said cam shaft, said latter cam having symmetrical ascending and descending operating cam surfaces substantially joined at their upper ends and a circular cam surface concentric with said shaft joining their lower ends, a fuel pump having a member reciprocable in a line substantially perpendicular to said cam shaft, a fuel pump tappet hingedly connected at one end to said reciprocable member, a roller rotatably mounted on the other end of said tappet and engaging said fuel pump cam, an exhaust valve operating member having a portion reciprocable approximately in a line perpendicular to said cam shaft, an exhaust valve tappet hingedly connected at one end to said portion of the exhaust valve operating member, a roller rotatably mounted on the other end of said exhaust valve tappet and engaging said exhaust Valve cam, an oscillatable control shaft parallel to said cam shaft, two arms on said control shaft, linkage connecting said arms respectively with the roller ends of said tappets to swing said tappets from one to another of two operative positions disposed on opposite sides of straight lines joining the hinged ends of said tappets respectively with the axis of said cam shaft upon predetermined angular movement of said control shaft, the effective length of one of said arms being greater than that of the other, whereby one of said tappets is moved through a greater angular displacement than the other by the same angular movement of the control shaft.

OVE PETERSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 828,064 Slater Aug. 7, 1906 880,050 Sulzer Feb. 25, 1908 935,500 Hennig Sept. 28, 1909 1,061,308 McKee May 13, 1918 1,294,077 Frenchelle Feb. 11, 1919 1,359,500 Guyot-Sionnest Nov. 23, 1920 2,000,555 Becker May 7, 1935 2,006,976 Woolson July 2, 1935 FOREIGN PATENTS Number Country Date 836 Great Britain Jan. 10, 1913 104,884 Great Britain June 28, 1917 

